/Engine/Source/Runtime/Core/Public/Misc/CString.h
make sure code usingFCString::Sprintfallocates enough (>= MAX_SPRINTF) memory for the destination buffer
template<typename FmtType, typename... Types> static int32 Sprintf ( [CharType](API\Runtime\Core\Misc\TCString\CharType) * Dest, const FmtType & Fmt, Types... Args )